Great amounts of digitalized information resources are offered online, and digital work piracy and possible infringement of the legal rights associated with the data resources offered on online are growing and serious concern to the data resource owners. As such, the manner of network resource utilization and the means for data transmission are restricted in order to protect the interests of the right holders and to prevent illegal replication of the network resources.
Two well-known methods of network data resource utilization for preventing network data resources from being copied and decrypted are shown in FIGS. 1-2. The first method as shown in FIG. 1 is a process involving authenticating a logged-in user, and transmitting encrypted data resources to the authenticated user with a time period of validity preset to the encrypted data resources designed to prevent the data resources from being illegally copied after the initial download. In this method, the identity of a user is first authenticated in a “user login” process to prevent unauthorized users from entering the system. The authenticated user may then search on a data resource platform to find the needed data resources. Thereafter, the found data resources are downloaded (payment may be required for some resources) into the user's local machine in the form of a file or a temporary directory. When the user needs to use the data resources, an invoke command is used to access the data resources. This conventional method presets an expiration time to the downloaded data resources such that the data resources will no longer be available to a user after a lapse of a preset expiration time since the initial downloading of the data resources. In this method, copying of the data resources is restricted by bundling the downloaded data resources with the user's machine, and the availability of the data resources is limited by a preset expiration time compared with the on-going time of the user's machine, which would then determines the period of availability of the downloaded data resources. Although this method provides some measure of protection from illegal replication, this conventional method has a defect in that the data resources will be free to be decrypted and copied once the data resources are fully downloaded into the user's machine (e.g., a personal computer) and saved in the local hard disk drive. As a result, the copyright of the data resources is still beyond protection according to this conventional method.
FIG. 2 shows another conventional method of accessing data resources over a network intended for preventing the network data resources from unauthorized replication and decryption. In this conventional method, the data resources are provided in a form of data streams as in a typical streaming media method, instead of downloading and storing in a local machine. A streaming media is a continuous time based media in the Internet that utilizes a streaming transmission technique, which is the key technique for achieving the streaming media. The streaming media technology enables a constant-rate transmission of the data from a transmitting end to a receiving end and enables the receiving end to process the data during transmission without having to wait for the entire transmission to complete. The second method as shown in FIG. 2 is different from the first method of FIG. 1 in that the data resources are not fully downloaded into a local machine but instead are cached in the system memory of the local machine. Thus, the second conventional method involves a process requiring a continuous downloading of data and caching of the data for use by a user. The data resources are not saved in the hard disk of a local machine or in any other storage device for later use but are instead temporarily stored in the system memory and are then deleted from the system memory after terminating the process. The second conventional method adopts a Digital Rights Management (DRM) technology (e.g., inserting anti-replication codes into digital network resources) intended for preventing the data resources from unauthorized copying and decryption after a user download, thereby to limit the illegal replication of the data resources to some extent.
However, when data resources are provided in data streams, encryption schemes for the data resources are limited. The most commonly adopted encryption scheme is the data header encryption, which allows continuous data resource download and utilization by a user once the user terminal has gone through the data header authentication. In a data header encryption, a whole data file can be obtained only if the data header is decrypted. In addition, utilization of the data resources by programs on a user terminal may also be subjected to the network conditions.